Sprayers are trailer devices for applying liquid chemicals to a field surface. The sprayer includes a central cart for supporting the supply tanks and a pair of hinged booms or wings which support nozzles in spaced apart arrangement connected to the supply tank. The nozzles and associated chemical supply lines are carried on a secondary boom rotationally supported on the primary boom at the rear in the operational direction. The primary boom is in rolling contact with the ground on caster wheels and carries all the hydraulic operational drive lines.
The wings are arranged in transverse position in operation to deliver chemical to a wide path with each pass. In operation the nozzles are directed downward toward the ground surface and may be shielded by windscreens. For transportation when not in use, the long wings fold behind the central cart. In transport position, the nozzles, supply lines and windscreens are rotated up above the booms to avoid damage. Hydraulic drive lines powered by the towing tractor are used to operate the setup sequence from transport position to operational position and back.
From an operational position, the folding sequence involves rotating the secondary booms from a downwardly directed position to an upwardly directed position. Once the secondary booms have been raised, the primary booms are folded back into a trailing position with the secondary booms of each side adjacent each other. The booms are aligned closely together to conform to a dimension which can be trailed on the highway. It is essential to raise the secondary boom before closing the primary booms as the close position in transport would cause the secondary booms to crash together. The rotation of the secondary boom thus also assists in adapting the device to a sufficiently narrow transport position.
As the booms close into the trailing position, the wheels are automatically locked in a forward rolling position by a cam which positions a locking pin in cooperating support plates. This is necessary for the booms to trail straight behind the tractor and cart. Depending on the length of the booms the number of wheels will vary. For very long booms, only the intermediate wheels are locked, while the rear wheels are still free to caster.
The setup unfolding sequence to return from a transport position to an operational position first requires the wheels to be unlocked to permit them to freely caster. The wings are advanced to their transverse position by a separate hydraulic drive. Rotation of the secondary boom is then completed to lower it into operational position. For some sprayers without the second hydraulic drive, the wheels have a two stage locking mechanism, which at a first stage is released to caster in a limited angular range. The tractor is then reversed with the controlled wheel positions assisting in opening the wings. Once in position further rotation of the secondary boom releases the wheels to caster freely and lowers the nozzles into operational position.
Since the booms are extremely long and heavy, these sequences of set-up and take-down are powered by hydraulic drive lines from the tractor. For positioning and removing the locking pins for the castor wheels, leverage on the cam for each wheel is obtained simultaneously by hydraulically rotating the secondary booms. However, when the operator is releasing the wheel lock in the transport position, the secondary booms of either side are closely adjacent. If the operator in the tractor misjudges the rotation to release the wheel locks, the secondary booms may be lowered too far and crash into each other. This results in damage to expensive windscreens, nozzles, and supply lines.
Precise positioning is particularly necessary for the two stage wheel locking mechanism and more difficult to judge by eye. While the two stage wheel lock is particularly advantageous for assisting in opening the wings, judging the degree of rotation needed to activate the first release stage, without over-rotating to the second, fully released, stage has proven too difficult to determine visually to take advantage of this type of wheel lock.
Other mechanisms have been proposed, such as U.S. Pat. No. 4,944,355 issued to Karchewski in 1990, for positioning the caster wheels for improved unfolding sequence. This device uses an additional hydraulic cylinder system for positioning the wheels in the setup position. This prior art system adds an additional setup step as well as more expensive and higher maintenance elements. It would be preferred to achieve the wheel positioning mechanically within the setup procedure.
It is desired to provide an apparatus and method to automate the setup steps in the operational sequence to avoid the possibility of error or damage.
It is an object of the invention to provide a mechanism for stopping the rotation of the secondary booms in the transport position once the locking pins have been released.
It is a further object of the invention to provide a means for automating a two stage wheel lock release to facilitate the wing opening step.